The invention relates generally to the field of power over local area networks, particularly Ethernet based networks, and more particularly to a method of classification over a plurality of paths.
The growth of local and wide area networks based on Ethernet technology has been an important driver for cabling offices and homes with structured cabling systems having multiple twisted wire pairs. The ubiquitous local area network, and the equipment which operates thereon, has led to a situation where there is often a need to attach a network operated device for which power is to be advantageously supplied by the network over the network wiring. Supplying power over the network wiring has many advantages including, but not limited to; reduced cost of installation; centralized power and power back-up; and centralized security and management.
The IEEE 802.3af-2003 standard, whose contents are incorporated herein by reference, is addressed to powering remote devices over an Ethernet based network. The above standard is limited to a powered device (PD) having a maximum power requirement during operation of 12.95 watts. Power can be delivered to the PD either directly from the switch/hub known as an endpoint power sourcing equipment (PSE) or alternatively via a midspan PSE. Unfortunately, no provision has been made in the above standard for PDs requiring power in excess of the above maximum power requirement. It is understood by those skilled in the art, that the above power limitation is primarily a function of the power carrying capabilities of the installed twisted wire pairs being utilized to deliver power. The above mentioned standard further prescribes a method of classification having a total of 5 power levels of which classes 0, 3 and 4 result in a maximum power level of 15.4 at the PSE which is equivalent to the aforementioned 12.95 watt limit.
Several patents addressed to the issue of supplying power to a PD over an Ethernet based network exist including: U.S. Pat. No. 6,473,608 issued to Lehr et al., whose contents are incorporated herein by reference; U.S. Pat. No. 6,643,1066 issued to Lehr et al., whose contents are incorporated herein by reference; and U.S. Pat. No. 6,1110,468 issued to De Nicolo whose contents are incorporated herein by reference.
It would therefore be desirable to have an architecture enabling powering remote devices over an Ethernet network having high power needs, and preferably having a classification system extending beyond that of the above standard.